Yes.
PR is here:
https://github.com/koreader/koreader/pull/2349
You need to use this (you point either to file of directory):
["suspend_screensaver"] = {
["path"] = "/mnt/onboard/.screensaver/sleeping"
},
["poweroff_screensaver"] = {
["path"] = "/mnt/onboard/.screensaver/powered_off"
},
mind syntax and backup settings.reader.lua before you change it in any way less not loose settings.